When studying the connection between fruits, vegetables, and health, it helps to talk about groups of plants. One of the most common classiﬁcation schemes is by “family.”
Those plant families you usually ﬁnd in the market or on the table include the following:
• The crucifer family (Cruciferae), which gets its name from the tiny cross you can see if you look at a recently sprouted seed. It includes a number of those vegetables that children (and some adults) instinctively but unwisely avoid—broccoli, Brussels sprouts, cabbage, cauliﬂower, collard greens, kale, kohlrabi, mustard greens, radishes, rutabaga, turnips, and watercress. Members of the crucifer family are excellent sources of isothiocyanates, indoles, thiocyanates, and nitriles, chemicals that may protect against some cancers.
• The melon/squash family (Cucurbitaceae) includes cucumbers, summer squashes such as zucchini and pumpkin, winter squashes such as acorn and butternut, and cantaloupes and honeydew melons.
• The legume family (Leguminoseae) includes alfalfa sprouts, beans, peas, and soybeans. Legumes have plenty of ﬁber, folate, and substances called protease inhibitors, all of which may oﬀer some protection against heart disease and cancer.
• The lily family (Liliaceae) includes asparagus, chives, garlic, leeks, onions, and shallots. These vegetables contain a number of sulfur-containing compounds, especially allicin and diallyl sulfate, that may ﬁght cancer.
• The citrus family (Rutaceae) encompasses grapefruits, lemons, limes, oranges, and tangerines. Citrus fruits are high in vitamin C and also contain the compounds limonene and coumarin, which have been shown to have anticancer properties in laboratory animals.
• Members of the solanum family (Solanaceae) include eggplant, peppers, potatoes, and tomatoes. As you can see from the list, this is a very diverse group. Tomatoes contain high amounts of lycopene, a type of antioxidant (see page 176) that may play a key role in preventing prostate and other cancers.
• The umbels (Umbelliferae) include carrots, celeriac, celery, parsley, and parsnips. Carrots are an excellent source of beta-carotene, which the body uses to make vitamin A. Several studies have also raised the possibility that beta-carotene and other related compounds called carotenoids help prevent some cancers or heart disease and maintain memory into old age.
While any one fruit or vegetable contains dozens, maybe hundreds, of diﬀerent compounds that your body uses for something besides energy, no single fruit or vegetable contains all of the substances you need. That’s why it’s a good idea to get a few servings a week from each of these major groups.
It’s also a good idea to eat for color variety as well. Painting your diet with the bold colors of ripe red tomatoes, crisp orange carrots, creamy yellow squash, emerald-green spinach, juicy blueberries, indigo plums, violet eggplants, and all shades in between not only makes meals more appealing but also ensures that you get a variety of beneﬁcial phytonutrients.
USDA AND OTHER GUIDELINES GIVE LITTLE REAL GUIDANCE
Back in 1991, the National Cancer Institute launched its 5-a- Day public health campaign. Through grocery store banners, labels on fruits and vegetables, public service announcements in the media, and educational materials for school-children, it urges us to eat ﬁve servings of fruits/vegetables a day. This campaign, which is still going strong, has been incorporated into the Dietary Guidelines for Americans, as well as into guidelines from the American Heart Association, American Cancer Society, World Health Organization, and others.
Five a day is a good start. But it gives no real guidance on what qualiﬁes for ﬁve a day. Two glasses of orange juice, an apple, an order of French fries at lunch, and a potato with dinner meets the 5-a-Day target. While that’s better than no fruits and vegetables at all, it doesn’t oﬀer the full dose of health beneﬁts described here.
Instead, use ﬁve a day as a minimum, not a goal. Don’t include potatoes in your daily tally. And try to vary the fruits and vegetables in your diet.
NOT MEASURING UP
Few of us take advantage of the incredible bounty of fruits and vegetables grown in this country and elsewhere. The average American relies on roughly a dozen diﬀerent fruits and vegetables. Daily consumption is just as limited, hovering around four servings a day, and that ﬁgure is vastly inﬂated by potatoes. A recent national survey showed that fewer than one in three of us gets ﬁve servings of fruits and vegetables a day. This limited consumption is a pity, given the clear-cut beneﬁts of eating fruits and vegetables.
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FRUITS AND VEGETABLES PREVENT CARDIOVASCULAR DISEASE
A diet that includes plenty of fruits and vegetables can help control or even prevent two of the main precursors of heart disease and stroke, high blood pressure and high cholesterol. Even better, investing in a plant-rich diet pays oﬀ in terms of lower chances of developing several forms of heart disease and stroke.
The protective beneﬁt, while not huge, is well worth the small eﬀort of adding more fruits and vegetables to your diet. By combining the results of seventeen large, long-term studies, researchers estimated that people in the top tier of fruit and vegetable consumption (about thirty-ﬁve servings a week, or your basic ﬁve a day) are 15 percent less likely to have a heart attack or other problem caused by restricted blood ﬂow to the heart muscle than those in the bottom tier. Among more than one hundred thousand men and women participating in the Nurses’ Health Study and the Health Professionals Follow-up Study, we found that eating about thirty servings of fruits and vegetables a week (or just under ﬁve a day) was associated with a 30 percent lower risk of the most common type of stroke (ischemic stroke), the kind caused by a blood clot blocking an artery in, or to, the brain. We calculated that eating one extra serving of fruits or vegetables a day decreases the chances of having an ischemic stroke by about 6 percent. In this study, most of the beneﬁt seemed to come from eating broccoli, spinach, kale, romaine lettuce, and citrus fruit or juice.